As electronic technologies progress, all kinds of electronic devices are steadily becoming a part of everyday life in a modern society. Many consumer electronic products, such as televisions, digital video disc (DVD) players, and multi-function digital media players are being extensively utilized by the public. In order to allow a user to enable selected functions of the consumer electronic products, many consumer electronic products rely on a remote control.
A conventional infrared (IR) remote control system allows one-to-one control of the electronic device. In other words, every electronic device must have its own corresponding remote control. Further, each function that the remote control manages is governed by a remote control signal that contains information associated with the function. The remote control has many buttons, each of which controls one of the functions. To enable or initiate a certain function of the electronic device, one must press the corresponding button to send the remote control signal containing the information associated with that function. When the electronic device receives the remote control signal, the electronic device extracts the information from the remote control signal and performs the function corresponding to the information in the remote control signal.
Generally speaking, the remote control employs either infrared or radio frequency technology for transmission. Apart from providing omnidirectional transmission, the radio frequency technology is also bi-directional, meaning that it not only sends but is also capable of receiving signals containing, e.g., status information of household appliances to display the same on a display of the remote control. Infrared technology has advantages of having a smaller size, lower power consumption and low cost. Thus, remote controls that employ infrared technology are dominant in the remote control market.
FIG. 1 is a diagram of a conventional infrared remote control system 10. The infrared remote control system 10 comprises a transmitting end 12 and a receiving end 14. The transmitting end 12 comprises an input interface 120, an encoding module 122, and an infrared transmitter 126. The receiving end 14 comprises an infrared receiver 140, a control module 144, and a function module 146. At the transmitting end 12, the input interface 120 comprises a plurality of buttons corresponding to different functions, and one can press the buttons to perform functions of the electronic device. The encoding module 122 converts an output of the input interface 120 to a binary signal, which may include a header or padding bits according to a predetermined rule in order to produce a packet complying with a predetermined format. The packet is then transmitted to the receiving end 14 through an infrared beam by the infrared transmitter 126. At the receiving end 14, the infrared receiver 140 converts the infrared beam from the infrared transmitter 126 to an electronic signal through an optical-to-electrical conversion process. The control module 144 comprises a microcontroller 148 and a memory 150 for demodulating, decoding, and identifying the control signal sent by the transmitting end 12. The control module 144 down-converts the control signal carried by the infrared beam to a baseband signal in order to identify a control command from the transmitting end 12 and to execute corresponding functions F(1) . . . F(n) associated with the control command through the function module 146.
In the infrared remote control system 10, since only a small amount of information is transmitted from the transmitting end 12 to the receiving end 14, accuracy is the most important consideration when transmitting the information. Many encoding standards have been developed in the prior art. The most prevalent standards are RC-5 standard and RECS80 standard in Europe, and NEC standard in Asia. Additionally, many consumer electronics manufacturers including as Mitsubishi, Panasonic, and JVC, have developed their own proprietary encoding schemes. These encoding schemes can be roughly divided into three modulation methods: phase modulation, pulse width modulation, and pulse position modulation. FIGS. 2-4 are waveforms corresponding to phase modulation, pulse width modulation, and pulse position modulation, respectively. Phase modulation represents a falling edge within a unit time interval by a “0” and a rising edge within the unit time interval by a “1”. In pulse width modulation, the pulse width determines a “0” and a “1” by a ratio of the high level to the low level for a transmitted infrared carrier modulation (a working period). For example, in the NEC encoding standard, “0” represents a pulse that is at the high level for 0.56 ms and at the low level for 0.56 ms, and “1” represents a pulse that is at the high level for 0.56 ms and at the low level for 1.68 ms. Thus, pulse position modulation represents pulses occurring in different positions relative to a reference pulse position by “0” and “1”.
In view of the above modulation methods, the control module 144 requires different demodulation and decoding methods to obtain the control command sent by the transmitting end 12. Taking the pulse width modulation as an example, the microcontroller 148 of the control module 144 uses an internal clock to measure a high period and a low period to identify “0” and “1” of the received signal. In other words, a decoding process according to the prior art requires the internal clock of the microcontroller 148. Generally speaking, in multimedia devices, in addition to demodulation and decoding, the microcontroller 148 is also used for video and audio processing. Thus, in the prior art, due to the resource consumption on the microcontroller 148 by the internal clock needed for the decoding process, the efficiency of the video and audio processing performed by the microcontroller 148 is lowered while also deteriorating the multimedia output quality. Further, unsatisfactory design flexibility is allowed for system manufacturers in view that many of the above decoding standards are realized by the conventional remote control system developed from proprietary hardware. For example, since infrared systems with proprietary decoding schemes are implemented by system manufacturers, an infrared receiver required by LCD televisions that are sold all over the world may encounter standard compliance complications in different parts of the world.
Furthermore, modern electronic products strive for power saving. When the electronic product is in a “sleep” mode, it is desirable to reduce the system power consumption as much as possible. It is noted that, when the system is in the sleep mode, awaking the system through hardware is more power saving but less flexible than through software. More specifically, in the prior art, awaking the system through hardware requires different hardware structures corresponding to different remote control manufacturers, such that system manufacturers are given unsatisfactory flexibility and hardware failures may be caused. However, in the prior art, although awaking the system through software yields better flexibility as an advantage, power consumption in a standby mode meanwhile gets too large.
Hence, there is a desire for an improved universal infrared receiving apparatus and associated method.